Every diesel vehicle owner knows that the lifeblood of their engine is clean, high-quality fuel. But imagine that you are on a long drive, cruising comfortably at 70 mph on the highway, when suddenly your engine sputters, loses power, and eventually, you’re stranded on the side of the road.
With subtle warning signs like decreased fuel efficiency, power loss, and increased emissions, the risk of water getting into your diesel tank is not only an issue of performance. It is also a matter of safety and engine longevity.
To help you out, we’ve written a guide that delves into the dangers of water infiltrating your diesel tank. Read on if you’d like to find out more.
Water in Diesel Tank and Winter Woes
Winter brings its own set of challenges for diesel-powered vehicles. Diesel fuel, when exposed to colder temperatures, has a tendency to gel or even wax. When water finds its way into a diesel tank, it exacerbates this problem.
Water freezes at a higher temperature than diesel fuel, forming ice crystals that can block fuel lines and filters. This results in poor fuel flow to the engine. Therefore, your vehicle might struggle to start or even stall in the middle of your journey.
More Dangerous Than Water in Regular Gasoline
Water contamination is never good for any fuel system. But the implications are far more severe when water enters a diesel tank. Diesel fuel is less refined than gasoline and has a heavier composition. As a result, it’s more susceptible to contamination.
When water infiltrates a diesel tank, it doesn’t mix with the fuel. Instead, it sinks to the bottom because of its higher density. Over time, this accumulated water can lead to severe engine damage due to hydrostatic shock. This is a sudden change in pressure caused by the rapid introduction of water into the cylinders.
Creating Conditions for Algae and Rust
The presence of water in a diesel tank creates an ideal environment for unwanted biological organisms like algae to thrive. Algae feed on the organic compounds in diesel fuel and proliferate in areas where water and fuel meet. These organisms, over time, can clog filters and degrade fuel quality.
Also, algae produce acidic byproducts that can cause corrosion and further contaminate the fuel.

Rust is another serious concern. Diesel tanks are typically made of metal, and water is a key ingredient for rust formation. When water infiltrates a diesel tank, it reacts with the metal, creating rust that can break off and contaminate the fuel. Over time, rust can also eat away at the tank walls, leading to leaks and fuel loss.
Multiplication of Microbes
Water in a diesel tank doesn’t only promote the growth of algae. It also provides a breeding ground for microbes. Microbes, like bacteria, multiply rapidly in warm, moist environments. They feed on the hydrocarbons in diesel fuel and water, creating a sticky, sludge-like substance. People often refer to this substance as a “diesel bug.”
This bio-contamination can cause numerous problems, from blocked fuel lines and reduced engine performance to complete engine failure in severe cases.
Prevention Steps to Take
Preventing water from getting into your diesel tank is crucial to maintain the efficiency and longevity of your engine. Here are some strategies that you should embrace.
Frequent Inspection
Regularly check your diesel tank for signs of water contamination. This includes checking for rust on the tank and monitoring changes in your vehicle’s performance.
Purchase Quality Fuel
Always buy your diesel fuel from reliable, reputable sources. Low-quality fuel may contain water and other contaminants.
Proper Storage
If you’re storing diesel fuel, make sure it’s in a clean, dry container. Also, avoid extreme temperature fluctuations to prevent condensation.
Fuel Additives
There are special additives available that can help disperse small amounts of water within the diesel fuel. They can prevent water from settling at the bottom of the tank, thus reducing the risk of engine damage.
Regular Tank Cleaning
Over time, sediments can accumulate at the bottom of your tank, which can trap water. Regular professional cleaning can prevent this accumulation.
What to Do if Water Is in Your Tank
If you suspect that water has entered your diesel tank, it’s important to act quickly to mitigate potential damage. First, stop driving your vehicle immediately to prevent water from entering the engine.
Next, you’ll need to confirm the presence of water. One of the easiest ways to do this is by using diesel fuel test kits. These kits are designed to detect water and other contaminants in your fuel. They are easy to use and provide reliable results. If the test comes back positive, it means water is present in your tank. Once confirmed, don’t attempt to start your vehicle. Starting the engine could force water into the fuel system.
Instead, drain the tank completely. This should be done by a professional to ensure all water is removed. After draining, refill the tank with fresh, high-quality diesel fuel. Finally, replace your fuel filter, as it may also be contaminated with water.
In severe cases, water contamination may damage the fuel injectors or the entire fuel system. In these instances, you’ll need to have your vehicle inspected and repaired by a professional mechanic.
The Dangers of Water in a Diesel Tank
It is important for diesel truck operators to understand the dangers of water getting into a diesel tank. Not only does water create a breeding ground for algae and microorganisms, but it also causes metal components to rust. The good news is that there are several simple things you can do to prevent water from getting into your fuel tank.
Do you want to find out more about how to keep your automobile’s engine in great condition? If so, make sure to check out the Automotive section of our website.